1. Field of the Invention
The invention relates to the field of production of radionuclides from Z-pinch machines.
2. Description of the Prior Art
Radionuclides are used in the medical field for both diagnostic and therapeutic purposes and there are other applications where radionuclides are used commonly. At present radionuclides are produced in research-based nuclear (fission) reactors, for which production is limited, hazardous, inconvenient and expensive. Commonly used medical radionuclides have a half-life of the order of minutes, which poses other problems for transportation and handling.
The reactor requires transuranic nuclear fuel elements to power the reactors. The reactor is expensive to operate and maintain, and requires highly specialized expertise. There are issues related to nuclear proliferation and security. Nuclear reactors are costly (>$10's M US), and only a limited number of research-based reactors are used for radionuclide production.
The growing need for radionuclides in the medical field and elsewhere is attractive, particularly for a small machine that can produce neutrons at the location of use, since many of the commonly used radionuclides have short radioactive half-lives. Neutron activated radionuclides could be used for both therapeutic and diagnostic purposes. The dosage mass could be in micro-to-milligram levels. The radionuclide could be used for variety of diseases related to heart and cancer. For the past decades virtually 1 out of 3 heart and cancer patients have received or been treated with radionuclides.
Every major hospital in the United States has a nuclear medicine department in which radionuclides are used to diagnose and treat a wide variety of diseases more effectively and safely by “seeing” how the disease process alters the normal function of an organ. To obtain this information, a patient either swallows, inhales, or receives an injection of a tiny amount of a radionuclide. Special cameras reveal where the radioactivity accumulates briefly in the body, providing, for example, an image of the heart that shows normal and malfunctioning tissue.
Radionuclides are also used in laboratory tests to measure important substances in the body, such as thyroid hormone. Radionuclides are used to effectively treat patients with thyroid diseases, including Graves disease, one of the most common forms of hyperthyroidism {and thyroid cancer. The use of ionizing radiation has led to major improvements in the diagnosis and treatment of patients with cancer. These innovations have resulted in increased survival rates and improved quality of life. Mammography can detect breast cancer at an early stage when it may be curable. Needle biopsies are more safe, accurate, and informative when guided by x-ray or other imaging techniques. Radiation is used in monitoring the response of tumors to treatment and in distinguishing malignant tumors from benign ones. Bone and liver scans can detect cancers that have spread. Half of all people with cancer are treated with radiation, and the number of those who have been cured continues to rise. There are now tens of thousands of individuals alive and cured from various cancers as a result of radiotherapy. In addition, there are many patients who have had their disease temporarily halted by radiotherapy. Radionuclides are also being used to decrease or eliminate the pain associated with cancer, such as that of the prostate or breast that has spread to the bone. Radionuclides are a technological backbone for much of the biomedical research being done today. They are used in identifying and learning how genes work. Much of the re-search on AIDS is dependent upon the use of radionuclides. Scientists are also “arming” monoclonal antibodies that are produced in the laboratory and engineered to bind to a specific protein on a patient's tumor cells with radionuclides. When such “armed” anti-bodies are injected into a patient, they bind to the tumor cells, which are then killed by the attached radioactivity, but the nearby normal cells are spared. So far, this approach has produced encouraging success in treating patients with leukemia.
Most new drugs, before they are approved by the Food and Drug Administration, have undergone animal studies that use radionuclides to learn how the body metabolizes them. Most of the radionuclides used in pharmaceutical industry are produced in the research nuclear reactors by neutron activation method. Conventional nuclear reactor is a copious source of neutron with energy ranging from less than eV to several MeV. The energy of thermal and epithermal neutrons range from 0.025-0.2 eV which can be absorbed by the nucleus to become a radioactive nucleus. The higher energy neutrons need to be thermalized using moderators made of polyurethane, graphite, water or heavy water. Due to a wide spectrum in energy of the neutrons produced in a reactor it is very hard to place the sample at a proper location for effective neutron activations which requires a minimum flux of 1010 cm−2 sec−1.
What is needed is a source of radionuclides that overcomes each of the drawbacks of the prior art production methods and apparatus and still fulfills the same production needs.